1
|
Ehweiner A, Duch C, Brembs B. Wings of Change: aPKC/FoxP-dependent plasticity in steering motor neurons underlies operant self-learning in Drosophila. F1000Res 2024; 13:116. [PMID: 38779314 PMCID: PMC11109550 DOI: 10.12688/f1000research.146347.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/31/2024] [Indexed: 05/25/2024] Open
Abstract
Background Motor learning is central to human existence, such as learning to speak or walk, sports moves, or rehabilitation after injury. Evidence suggests that all forms of motor learning share an evolutionarily conserved molecular plasticity pathway. Here, we present novel insights into the neural processes underlying operant self-learning, a form of motor learning in the fruit fly Drosophila. Methods We operantly trained wild type and transgenic Drosophila fruit flies, tethered at the torque meter, in a motor learning task that required them to initiate and maintain turning maneuvers around their vertical body axis (yaw torque). We combined this behavioral experiment with transgenic peptide expression, CRISPR/Cas9-mediated, spatio-temporally controlled gene knock-out and confocal microscopy. Results We find that expression of atypical protein kinase C (aPKC) in direct wing steering motoneurons co-expressing the transcription factor FoxP is necessary for this type of motor learning and that aPKC likely acts via non-canonical pathways. We also found that it takes more than a week for CRISPR/Cas9-mediated knockout of FoxP in adult animals to impair motor learning, suggesting that adult FoxP expression is required for operant self-learning. Conclusions Our experiments suggest that, for operant self-learning, a type of motor learning in Drosophila, co-expression of atypical protein kinase C (aPKC) and the transcription factor FoxP is necessary in direct wing steering motoneurons. Some of these neurons control the wing beat amplitude when generating optomotor responses, and we have discovered modulation of optomotor behavior after operant self-learning. We also discovered that aPKC likely acts via non-canonical pathways and that FoxP expression is also required in adult flies.
Collapse
Affiliation(s)
- Andreas Ehweiner
- Institut für Zoologie - Neurogenetik, Universität Regensburg, Regensburg, Bavaria, 93040, Germany
| | - Carsten Duch
- Institute of Developmental Biology and Neurobiology (iDN), Johannes Gutenberg Universitat Mainz, Mainz, Rhineland-Palatinate, Germany
| | - Björn Brembs
- Institut für Zoologie - Neurogenetik, Universität Regensburg, Regensburg, Bavaria, 93040, Germany
| |
Collapse
|
2
|
Wong E, Anggono V, Williams SR, Degnan SM, Degnan BM. Phototransduction in a marine sponge provides insights into the origin of animal vision. iScience 2022; 25:104436. [PMID: 35707725 PMCID: PMC9189025 DOI: 10.1016/j.isci.2022.104436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 08/22/2021] [Accepted: 05/17/2022] [Indexed: 11/24/2022] Open
Abstract
Most organisms respond to light. Here, we investigate the origin of metazoan phototransduction by comparing well-characterized opsin-based photosystems in neural animals with those in the sponge Amphimedon queenslandica. Although sponges lack neurons and opsins, they can respond rapidly to light. In Amphimedon larvae, this is guided by the light-sensing posterior pigment ring. We first use cell-type-specific transcriptomes to reveal that genes that characterize eumetazoan Gt- and Go-mediated photosystems are enriched in the pigment ring. We then apply a suite of signaling pathway agonists and antagonists to swimming larvae exposed to directional light. These experiments implicate metabotropic glutamate receptors, phospholipase-C, protein kinase C, and voltage-gated calcium channels in larval phototaxis; the inhibition of phospholipase-C, a key transducer of the Gq-mediated pathway, completely reverses phototactic behavior. Together, these results are consistent with aneural sponges sharing with neural metazoans an ancestral set of photosignaling pathways. Amphimedon larvae are negatively phototactic but lack neurons and opsins Sponge larval photosensory cells are enriched in conserved phototransduction genes Conserved photosignaling pathways appear to be controlling larval phototaxis Phototactic behavior is reversed by the inhibition of phospholipase-C
Collapse
Affiliation(s)
- Eunice Wong
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Victor Anggono
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia.,Clem Jones Centre for Ageing Dementia Research, University of Queensland, Brisbane, QLD 4072, Australia
| | - Stephen R Williams
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia
| | - Sandie M Degnan
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Bernard M Degnan
- School of Biological Sciences, University of Queensland, Brisbane, QLD 4072, Australia
| |
Collapse
|
3
|
Farah CA, Dunn TW, Hastings MH, Ferguson L, Gao C, Gong K, Sossin WS. A role for Numb in Protein kinase M (PKM)-mediated increase in surface AMPA receptors during facilitation in Aplysia. J Neurochem 2019; 150:366-384. [PMID: 31254393 DOI: 10.1111/jnc.14807] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/25/2019] [Accepted: 06/26/2019] [Indexed: 12/15/2022]
Abstract
There is considerable evidence from both vertebrates and invertebrates that persistently active protein kinases maintain changes in synaptic strength that underlie memory. In the hermaphrodite marine mollusk, Aplysia californica, truncated forms of protein kinase C (PKC) termed protein kinase Ms have been implicated in both intermediate- and long-term facilitation, an increase in synaptic strength between sensory neurons and motor neurons thought to underlie behavioural sensitization in the animal. However, few substrates have been identified as candidates that could mediate this increase in synaptic strength. PKMs have been proposed to maintain synaptic strength through preventing endocytosis of AMPA receptors. Numb is a conserved regulator of endocytosis that is modulated by phosphorylation. We have identified and cloned Aplysia Numb (ApNumb). ApNumb contains three conserved PKC phosphorylation sites and PKMs generated from classical and atypical Aplysia PKCs can phosphorylate ApNumb in vitro and in cells. Over-expression of ApNumb that lacks the conserved PKC phosphorylation sites blocks increases in surface levels of a pHluorin-tagged Aplysia glutamate receptor measured using live imaging after intermediate- or long-term facilitation. Over-expression of this form of ApNumb did not block increases in synaptic strength seen during intermediate-term facilitation, but did block increases in synaptic strength seen during long-term facilitation. There was no effect of over-expression of this form of ApNumb on other putative Numb targets as measured using increases in calcium downstream of neurotrophins or agonists of metabotropic glutamate receptors. These results suggest that in Aplysia neurons, Numb specifically regulates AMPA receptor trafficking and is an attractive candidate for a target of PKMs in long-term maintenance of synaptic strength. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/.
Collapse
Affiliation(s)
- Carole A Farah
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Tyler W Dunn
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Margaret H Hastings
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Larissa Ferguson
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Cherry Gao
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Katrina Gong
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| |
Collapse
|
4
|
A Closely Associated Phospholipase C Regulates Cation Channel Function through Phosphoinositide Hydrolysis. J Neurosci 2018; 38:7622-7634. [PMID: 30037836 DOI: 10.1523/jneurosci.0586-18.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 06/28/2018] [Accepted: 07/17/2018] [Indexed: 11/21/2022] Open
Abstract
In the hemaphroditic sea snail, Aplysia californica, reproduction is initiated when the bag cell neurons secrete egg-laying hormone during a protracted afterdischarge. A source of depolarization for the afterdischarge is a voltage-gated, nonselective cation channel, similar to transient receptor potential (TRP) channels. Once the afterdischarge is triggered, phospholipase C (PLC) is activated to hydrolyze phosphatidylinositol-4,5-bisphosphate (PIP2) into diacylglycerol (DAG) and inositol trisphosphate (IP3). We previously reported that a DAG analog, 1-oleoyl-2-acetyl-sn-glycerol (OAG), activates a prominent, inward whole-cell cationic current that is enhanced by IP3 To examine the underlying mechanism, we investigated the effect of exogenous OAG and IP3, as well as PLC activation, on cation channel activity and voltage dependence in excised, inside-out patches from cultured bag cell neurons. OAG transiently elevated channel open probability (PO) when applied to excised patches; however, coapplication of IP3 prolonged the OAG-induced response. In patches exposed to OAG and IP3, channel voltage dependence was left-shifted; this was also observed with OAG, but not to the same extent. Introducing the PLC activator, m-3M3FBS, to patches increased channel PO, suggesting PLC may be physically linked to the channels. Accordingly, blocking PLC with U-73122 ablated the m-3M3FBS-induced elevation in PO Treatment with m-3M3FBS left-shifted cation channel voltage dependence to a greater extent than exogenous OAG and IP3 Finally, OAG and IP3 potentiated the stimulatory effect of PKC, which is also associated with the channel. Thus, the PLC-PKC signaling system is physically localized such that PIP2 breakdown products liberated during the afterdischarge modulate the cation channel and temporally influence neuronal activity.SIGNIFICANCE STATEMENT Using excised patches from Aplysia bag cell neurons, we present the first evidence of a nonselective cation channel physically associating with phospholipase C (PLC) at the single-channel level. PLC-mediated breakdown of phospholipids generates diacylglycerol and inositol trisphosphate, which activate the cation channel. This is mimicked by exogenous lipids; furthermore, these second messengers left-shift channel voltage dependence and enhance the response of the channel to protein kinase C. PLC-mediated lipid signaling controls single-channel currents to ensure depolarization is maintained for an extended period of firing, termed the afterdischarge, when the bag cell neurons secrete egg-laying hormone to trigger reproduction.
Collapse
|
5
|
Barroso-Flores J, Herrera-Valdez MA, Galarraga E, Bargas J. Models of Short-Term Synaptic Plasticity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1015:41-57. [PMID: 29080020 DOI: 10.1007/978-3-319-62817-2_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We focus on dynamical descriptions of short-term synaptic plasticity. Instead of focusing on the molecular machinery that has been reviewed recently by several authors, we concentrate on the dynamics and functional significance of synaptic plasticity, and review some mathematical models that reproduce different properties of the dynamics of short term synaptic plasticity that have been observed experimentally. The complexity and shortcomings of these models point to the need of simple, yet physiologically meaningful models. We propose a simplified model to be tested in synapses displaying different types of short-term plasticity.
Collapse
Affiliation(s)
- Janet Barroso-Flores
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico.
| | - Marco A Herrera-Valdez
- Departamento de Matemáticas, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico.
| | - Elvira Galarraga
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico
| | - José Bargas
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, DF, 04510, Mexico
| |
Collapse
|
6
|
Sturgeon RM, Magoski NS. Diacylglycerol-mediated regulation of Aplysia bag cell neuron excitability requires protein kinase C. J Physiol 2016; 594:5573-92. [PMID: 27198498 DOI: 10.1113/jp272152] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 05/17/2016] [Indexed: 01/15/2023] Open
Abstract
KEY POINTS In Aplysia, reproduction is initiated by the bag cell neurons and a prolonged period of enhanced excitability known as the afterdischarge. Phosphoinositide turnover is upregulated during the afterdischarge resulting in the hydrolysis of phosphatidylinositol-4,5-bisphosphate by phospholipase C (PLC) and the release of diacylglycerol (DAG) and inositol trisphosphate (IP3 ). In whole-cell voltage-clamped cultured bag cell neurons, 1-oleoyl-2-acetyl-sn-glycerol (OAG), a synthetic DAG analogue, activates a dose-dependent, transient, inward current (IOAG ) that is enhanced by IP3 , mimicked by PLC activation and dependent on basal protein kinase C (PKC) activity. OAG depolarizes bag cell neurons and triggers action potential firing in culture, and prolongs electrically stimulated afterdischarges in intact bag cell neuron clusters ex vivo. Although PKC alone cannot activate the current, it is required for IOAG ; this is the first description of required obligate PKC activity working in concert with PLC, DAG and IP3 to maintain the depolarization required for prolonged excitability in Aplysia reproduction. ABSTRACT Following synaptic input, the bag cell neurons of Aplysia undergo a long-term afterdischarge of action potentials to secrete egg-laying hormone and initiate reproduction. Early in the afterdischarge, phospholipase C (PLC) hydrolyses phosphatidylinositol-4,5-bisphosphate into inositol trisphosphate (IP3 ) and diacylglycerol (DAG). In Aplysia, little is known about the action of DAG, or any interaction with IP3 ; thus, we examined the effects of a synthetic DAG analogue, 1-oleoyl-2-acetyl-sn-glycerol (OAG), on whole-cell voltage-clamped cultured bag cell neurons. OAG induced a large, prolonged, Ca(2+) -permeable, concentration-dependent inward current (IOAG ) that reversed at ∼-20 mV and was enhanced by intracellular IP3 . A similar current was evoked by either another DAG analogue, 1,2-dioctanoyl-sn-glycerol (DOG), or activating PLC with N-(3-trifluoromethylphenyl)-2,4,6-trimethylbenzenesulfonamide (m-3M3FBS). IOAG was reduced by the general cation channel blockers Gd(3+) or flufenamic acid. Work in other systems indicated that OAG activates channels independently of protein kinase C (PKC); however, we found pretreating bag cell neurons with any of the PKC inhibitors bisindolylmaleimide, sphinganine, or H7, attenuated IOAG . However, stimulating PKC with phorbol 12-myristate 13-acetate (PMA) did not evoke current or enhance IOAG ; moreover, unlike PMA, OAG failed to trigger PKC, as confirmed by an independent bioassay. Finally, OAG or m-3M3FBS depolarized cultured neurons, and while OAG did not provoke afterdischarges from bag cell neurons in the nervous system, it did double the duration of synaptically elicited afterdischarges. To our knowledge, this is the first report of obligate PKC activity for IOAG gating. An interaction between phosphoinositol metabolites and PKC could control the cation channel to influence afterdischarge duration.
Collapse
Affiliation(s)
- Raymond M Sturgeon
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, ON, Canada, K7L 3N6
| | - Neil S Magoski
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, ON, Canada, K7L 3N6.
| |
Collapse
|
7
|
cJun and CREB2 in the postsynaptic neuron contribute to persistent long-term facilitation at a behaviorally relevant synapse. J Neurosci 2015; 35:386-95. [PMID: 25568130 DOI: 10.1523/jneurosci.3284-14.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Basic region leucine zipper (bZIP) transcription factors regulate gene expression critical for long-term synaptic plasticity or neuronal excitability contributing to learning and memory. At sensorimotor synapses of Aplysia, changes in activation or expression of CREB1 and CREB2 in sensory neurons are required for long-term synaptic plasticity. However, it is unknown whether concomitant stimulus-induced changes in expression and activation of bZIP transcription factors in the postsynaptic motor neuron also contribute to persistent long-term facilitation (P-LTF). We overexpressed various forms of CREB1, CREB2, or cJun in the postsynaptic motor neuron L7 in cell culture to examine whether these factors contribute to P-LTF. P-LTF is evoked by 2 consecutive days of 5-HT applications (2 5-HT), while a transient form of LTF is produced by 1 day of 5-HT applications (1 5-HT). Significant increases in the expression of both cJun and CREB2 mRNA in L7 accompany P-LTF. Overexpressing each bZIP factor in L7 did not alter basal synapse strength, while coexpressing cJun and CREB2 in L7 evoked persistent increases in basal synapse strength. In contrast, overexpressing cJun and CREB2 in sensory neurons evoked persistent decreases in basal synapse strength. Overexpressing wild-type cJun or CREB2, but not CREB1, in L7 can replace the second day of 5-HT applications in producing P-LTF. Reducing cJun activity in L7 blocked P-LTF evoked by 2 5-HT. These results suggest that expression and activation of different bZIP factors in both presynaptic and postsynaptic neurons contribute to persistent change in synapse strength including stimulus-dependent long-term synaptic plasticity.
Collapse
|
8
|
Chen S, Cai D, Pearce K, Sun PYW, Roberts AC, Glanzman DL. Reinstatement of long-term memory following erasure of its behavioral and synaptic expression in Aplysia. eLife 2014; 3:e03896. [PMID: 25402831 PMCID: PMC4270066 DOI: 10.7554/elife.03896] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 11/13/2014] [Indexed: 12/29/2022] Open
Abstract
Long-term memory (LTM) is believed to be stored in the brain as changes in synaptic connections. Here, we show that LTM storage and synaptic change can be dissociated. Cocultures of Aplysia sensory and motor neurons were trained with spaced pulses of serotonin, which induces long-term facilitation. Serotonin (5HT) triggered growth of new presynaptic varicosities, a synaptic mechanism of long-term sensitization. Following 5HT training, two antimnemonic treatments-reconsolidation blockade and inhibition of PKM--caused the number of presynaptic varicosities to revert to the original, pretraining value. Surprisingly, the final synaptic structure was not achieved by targeted retraction of the 5HT-induced varicosities but, rather, by an apparently arbitrary retraction of both 5HT-induced and original synapses. In addition, we find evidence that the LTM for sensitization persists covertly after its apparent elimination by the same antimnemonic treatments that erase learning-related synaptic growth. These results challenge the idea that stable synapses store long-term memories.
Collapse
Affiliation(s)
- Shanping Chen
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, United States
| | - Diancai Cai
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, United States
| | - Kaycey Pearce
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, United States
| | - Philip Y-W Sun
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, United States
| | - Adam C Roberts
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, United States
| | - David L Glanzman
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, United States
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, United States
- Integrative Center for Learning and Memory, Brain Research Institute, University of California, Los Angeles, Los Angeles, United States
| |
Collapse
|
9
|
Persistent long-term facilitation at an identified synapse becomes labile with activation of short-term heterosynaptic plasticity. J Neurosci 2014; 34:4776-85. [PMID: 24695698 DOI: 10.1523/jneurosci.0098-14.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Short-term and long-term synaptic plasticity are cellular correlates of learning and memory of different durations. Little is known, however, how these two forms of plasticity interact at the same synaptic connection. We examined the reciprocal impact of short-term heterosynaptic or homosynaptic plasticity at sensorimotor synapses of Aplysia in cell culture when expressing persistent long-term facilitation (P-LTF) evoked by serotonin [5-hydroxytryptamine (5-HT)]. Short-term heterosynaptic plasticity induced by 5-HT (facilitation) or the neuropeptide FMRFa (depression) and short-term homosynaptic plasticity induced by tetanus [post-tetanic potentiation (PTP)] or low-frequency stimulation [homosynaptic depression (HSD)] of the sensory neuron were expressed in both control synapses and synapses expressing P-LTF in the absence or presence of protein synthesis inhibitors. All forms of short-term plasticity failed to significantly affect ongoing P-LTF in the absence of protein synthesis inhibitors. However, P-LTF reversed to control levels when either 5-HT or FMRFa was applied in the presence of rapamycin. In contrast, P-LTF was unaffected when either PTP or HSD was evoked in the presence of either rapamycin or anisomycin. These results indicate that synapses expressing persistent plasticity acquire a "new" baseline and functionally express short-term changes as naive synapses, but the new baseline becomes labile following selective activations-heterosynaptic stimuli that evoke opposite forms of plasticity-such that when presented in the presence of protein synthesis inhibitors produce a rapid reversal of the persistent plasticity. Activity-selective induction of a labile state at synapses expressing persistent plasticity may facilitate the development of therapies for reversing inappropriate memories.
Collapse
|
10
|
Takahashi T, Takigami S, Sunada H, Lukowiak K, Sakakibara M. Critical period of memory enhancement during taste avoidance conditioning in Lymnaea stagnalis. PLoS One 2013; 8:e75276. [PMID: 24098373 PMCID: PMC3789661 DOI: 10.1371/journal.pone.0075276] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 08/14/2013] [Indexed: 01/06/2023] Open
Abstract
The present study investigated the optimal training procedure leading to long-lasting taste avoidance behavior in Lymnaea. A training procedure comprising 5 repeated pairings of a conditional stimulus (CS, sucrose), with an unconditional stimulus (US, a tactile stimulation to the animal's head), over a 4-day period resulted in an enhanced memory formation than 10 CS-US repeated pairings over a 2-day period or 20 CS-US repeated pairings on a single day. Backward conditioning (US-CS) pairings did not result in conditioning. Thus, this taste avoidance conditioning was CS-US pairing specific. Food avoidance behavior was not observed following training, however, if snails were immediately subjected to a cold-block (4°C for 10 min). It was critical that the cold-block be applied within 10 min to block long-term memory (LTM) formation. Further, exposure to the cold-block 180 min after training also blocked both STM and LTM formation. The effects of the cold-block on subsequent learning and memory formation were also examined. We found no long lasting effects of the cold-block on subsequent memory formation. If protein kinase C was activated before the conditioning paradigm, snails could still acquire STM despite exposure to the cold-block.
Collapse
Affiliation(s)
- Tomoyo Takahashi
- School of High-Technology for Human Welfare, Tokai University, Numazu, Shizuoka, Japan
| | - Satoshi Takigami
- Graduate School of High-Technology for Human Welfare, Tokai University, Numazu, Shizuoka, Japan
- Graduate School of Bioscience, Tokai University, Numazu, Shizuoka, Japan
| | - Hiroshi Sunada
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Canada
| | - Manabu Sakakibara
- School of High-Technology for Human Welfare, Tokai University, Numazu, Shizuoka, Japan
- Graduate School of High-Technology for Human Welfare, Tokai University, Numazu, Shizuoka, Japan
- Graduate School of Bioscience, Tokai University, Numazu, Shizuoka, Japan
- * E-mail:
| |
Collapse
|
11
|
Roles of Protein Kinase C and Protein Kinase M in Aplysia Learning. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/b978-0-12-415823-8.00018-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
12
|
Cai D, Pearce K, Chen S, Glanzman DL. Reconsolidation of long-term memory in Aplysia. Curr Biol 2012; 22:1783-8. [PMID: 22885063 DOI: 10.1016/j.cub.2012.07.038] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 06/15/2012] [Accepted: 07/16/2012] [Indexed: 10/28/2022]
Abstract
When an animal is reminded of a prior experience and shortly afterward treated with a protein synthesis inhibitor, the consolidated memory for the experience can be disrupted; by contrast, protein synthesis inhibition without prior reminding commonly does not disrupt long-term memory [1-3]. Such results imply that the reminding triggers reconsolidation of the memory. Here, we asked whether the behavioral and synaptic changes associated with the memory for long-term sensitization (LTS) of the siphon-withdrawal reflex in the marine snail Aplysia californica [4, 5] could undergo reconsolidation. In support of this idea, we found that when sensitized animals were given abbreviated reminder sensitization training 48-96 hr after the original sensitization training, followed by treatment with the protein synthesis inhibitor anisomycin, LTS was disrupted. We also found that long-term (≥ 24 hr) facilitation (LTF) [6], which can be induced in the monosynaptic connection between Aplysia sensory and motor neurons in dissociated cell culture by multiple spaced pulses of the endogenous facilitatory transmitter serotonin (5-HT) [7, 8], could be eliminated by treating the synapses with one reminder pulse of 5-HT, followed by anisomycin, at 48 hr after the original training. Our results provide a simple model system for understanding the synaptic basis of reconsolidation.
Collapse
Affiliation(s)
- Diancai Cai
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | | | | | | |
Collapse
|
13
|
Abstract
How the brain maintains long-term memories is one of the major outstanding questions in modern neuroscience. Evidence from mammalian studies indicates that activity of a protein kinase C (PKC) isoform, protein kinase Mζ (PKMζ), plays a critical role in the maintenance of long-term memory. But the range of memories whose persistence depends on PKMζ, and the mechanisms that underlie the effect of PKMζ on long-term memory, remain obscure. Recently, a PKM isoform, known as PKM Apl III, was cloned from the nervous system of Aplysia. Here, we tested whether PKM Apl III plays a critical role in long-term memory maintenance in Aplysia. Intrahemocoel injections of the pseudosubstrate inhibitory peptide ZIP (ζ inhibitory peptide) or the PKC inhibitor chelerythrine erased the memory for long-term sensitization (LTS) of the siphon-withdrawal reflex (SWR) as late as 7 d after training. In addition, both PKM inhibitors disrupted the maintenance of long-term (≥ 24 h) facilitation (LTF) of the sensorimotor synapse, a form of synaptic plasticity previously shown to mediate LTS of the SWR. Together with previous results (Bougie et al., 2009), our results support the idea that long-term memory in Aplysia is maintained via a positive-feedback loop involving PKM Apl III-dependent protein phosphorylation. The present data extend the known role of PKM in memory maintenance to a simple and well studied type of long-term learning. Furthermore, the demonstration that PKM activity underlies the persistence of LTF of the Aplysia sensorimotor synapse, a form of synaptic plasticity amenable to rigorous cellular and molecular analyses, should facilitate efforts to understand how PKM activity maintains memory.
Collapse
|
14
|
Tam AKH, Gardam KE, Lamb S, Kachoei BA, Magoski NS. Role for protein kinase C in controlling Aplysia bag cell neuron excitability. Neuroscience 2011; 179:41-55. [PMID: 21277944 DOI: 10.1016/j.neuroscience.2011.01.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 01/04/2011] [Accepted: 01/20/2011] [Indexed: 11/30/2022]
Abstract
Targeting signalling molecules to ion channels can expedite regulation and assure the proper transition of changes to excitability. In the bag cell neurons of Aplysia, single-channel studies of excised patches have revealed that protein kinase C (PKC) gates a non-selective cation channel through a close, physical association. This channel drives a prolonged afterdischarge and concomitant neuropeptide secretion to provoke reproductive behaviour. However, it is not clear if PKC alters cation channel function and/or the membrane potential at the whole-cell level. Afterdischarge-like depolarizations can be evoked in cultured bag cell neurons by bath-application of Conus textile venom (CtVm), which triggers the cation channel through an apparent intracellular pathway. The present study shows that the CtVm-induced depolarization was reduced by nearly 50% compared to control following dialysis with the G-protein blocker, guanosine-5'-O-2-thiodiphosphate (GDP-β-S), or treatment with either the phospholipase C inhibitor, 1-[6-[[(17β)-3-Methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122), or the PKC inhibitor, sphinganine. Neurons exposed to the PKC activator, phorbol 12-myristate 13-acetate (PMA), displayed depolarization with accompanying spiking, and were found to be far more responsive to depolarizing current injection versus control. Immunocytochemical staining for the two typical Aplysia PKC isoforms, Apl I and Apl II, revealed that both kinases were present in unstimulated cultured bag cell neurons. However, in CtVm-treated neurons, the staining intensity for PKC Apl I increased, peaking at 10 min post-application. Conversely, the intensity of PKC Apl II staining decreased over the duration of CtVm exposure. Our results suggest that the CtVm-induced depolarization involves PKC activation, and is consistent with prior work showing PKC closely-associating with the cation channel to produce the depolarization necessary for the afterdischarge and species propagation.
Collapse
Affiliation(s)
- A K H Tam
- Department of Physiology, Queen's University, Kingston, ON K7L 3N6, Canada
| | | | | | | | | |
Collapse
|
15
|
Jin I, Kandel ER, Hawkins RD. Whereas short-term facilitation is presynaptic, intermediate-term facilitation involves both presynaptic and postsynaptic protein kinases and protein synthesis. Learn Mem 2011; 18:96-102. [PMID: 21245210 DOI: 10.1101/lm.1949711] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Whereas short-term plasticity involves covalent modifications that are generally restricted to either presynaptic or postsynaptic structures, long-term plasticity involves the growth of new synapses, which by its nature involves both pre- and postsynaptic alterations. In addition, an intermediate-term stage of plasticity has been identified that might form a bridge between short- and long-term plasticity. Consistent with that idea, although short-term term behavioral sensitization in Aplysia involves presynaptic mechanisms, intermediate-term sensitization involves both pre- and postsynaptic mechanisms. However, it has not been known whether that is also true of facilitation in vitro, where a more detailed analysis of the mechanisms involved in the different stages and their interrelations is feasible. To address those questions, we have examined pre- and postsynaptic mechanisms of short- and intermediate-term facilitation at Aplysia sensory-motor neuron synapses in isolated cell culture. Whereas short-term facilitation by 1-min 5-HT involves presynaptic PKA and CamKII, intermediate-term facilitation by 10-min 5-HT involves presynaptic PKC and postsynaptic Ca(2+) and CamKII, as well as both pre- and postsynaptic protein synthesis. These results support the idea that the intermediate-term stage is the first to involve both pre- and postsynaptic molecular mechanisms, which could in turn serve as some of the initial steps in a cascade leading to synaptic growth during long-term plasticity.
Collapse
Affiliation(s)
- Iksung Jin
- Department of Neuroscience, Columbia University, New York, NY 10032, USA
| | | | | |
Collapse
|
16
|
Presynaptic and postsynaptic mechanisms of synaptic plasticity and metaplasticity during intermediate-term memory formation in Aplysia. J Neurosci 2010; 30:5781-91. [PMID: 20410130 DOI: 10.1523/jneurosci.4947-09.2010] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synaptic plasticity and learning involve different mechanisms depending on the following: (1) the stage of plasticity and (2) the history of plasticity, or metaplasticity. However, little is known about how these two factors are related. We have addressed that question by examining mechanisms of synaptic plasticity during short-term and intermediate-term behavioral sensitization and dishabituation in a semi-intact preparation of the Aplysia siphon-withdrawal reflex. Dishabituation differs from sensitization in that it is preceded by habituation, and is thus a paradigm for metaplasticity. We find that whereas facilitation during short-term sensitization by one tail shock involves presynaptic covalent modifications by protein kinase A (PKA) and CamKII, facilitation during intermediate-term sensitization by four shocks involves both presynaptic (PKA, CaMKII) and postsynaptic (Ca(2+), CaMKII) covalent modifications, as well as both presynaptic and postsynaptic protein synthesis. The facilitation also involves presynaptic spike broadening 2.5 min after either one or four shocks, but not at later times. Dishabituation by four shocks differs from sensitization in several ways. First, it does not involve PKA or CaMKII, but rather involves presynaptic PKC. In addition, unlike sensitization with the same shock, dishabituation by four shocks does not involve protein synthesis or presynaptic spike broadening, and it also does not involve postsynaptic Ca(2+). These results demonstrate that not only the mechanisms but also the site of plasticity depend on both the stage of plasticity and metaplasticity during memory formation.
Collapse
|
17
|
Sossin WS, Abrams TW. Evolutionary conservation of the signaling proteins upstream of cyclic AMP-dependent kinase and protein kinase C in gastropod mollusks. BRAIN, BEHAVIOR AND EVOLUTION 2009; 74:191-205. [PMID: 20029183 DOI: 10.1159/000258666] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The protein kinase C (PKC) and the cAMP-dependent kinase (protein kinase A; PKA) pathways are known to play important roles in behavioral plasticity and learning in the nervous systems of a wide variety of species across phyla. We briefly review the members of the PKC and PKA family and focus on the evolution of the immediate upstream activators of PKC and PKA i.e., phospholipase C (PLC) and adenylyl cyclase (AC), and their conservation in gastropod mollusks, taking advantage of the recent assembly of the Aplysiacalifornica and Lottia gigantea genomes. The diversity of PLC and AC family members present in mollusks suggests a multitude of possible mechanisms to activate PKA and PKC; we briefly discuss the relevance of these pathways to the known physiological activation of these kinases in Aplysia neurons during plasticity and learning. These multiple mechanisms of activation provide the gastropod nervous system with tremendous flexibility for implementing neuromodulatory responses to both neuronal activity and extracellular signals.
Collapse
Affiliation(s)
- Wayne S Sossin
- Department of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Montreal, Que., Canada.
| | | |
Collapse
|
18
|
Habituation in Aplysia: The Cheshire Cat of neurobiology. Neurobiol Learn Mem 2009; 92:147-54. [DOI: 10.1016/j.nlm.2009.03.005] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 03/17/2009] [Accepted: 03/19/2009] [Indexed: 11/27/2022]
|
19
|
Role of protein kinase C in the induction and maintenance of serotonin-dependent enhancement of the glutamate response in isolated siphon motor neurons of Aplysia californica. J Neurosci 2009; 29:5100-7. [PMID: 19386905 DOI: 10.1523/jneurosci.4149-08.2009] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Serotonin (5-HT) mediates learning-related facilitation of sensorimotor synapses in Aplysia californica. Under some circumstances 5-HT-dependent facilitation requires the activity of protein kinase C (PKC). One critical site of PKC's contribution to 5-HT-dependent synaptic facilitation is the presynaptic sensory neuron. Here, we provide evidence that postsynaptic PKC also contributes to synaptic facilitation. We investigated the contribution of PKC to enhancement of the glutamate-evoked potential (Glu-EP) in isolated siphon motor neurons in cell culture. A 10 min application of either 5-HT or phorbol ester, which activates PKC, produced persistent (> 50 min) enhancement of the Glu-EP. Chelerythrine and bisindolylmaleimide-1 (Bis), two inhibitors of PKC, both blocked the induction of 5-HT-dependent enhancement. An inhibitor of calpain, a calcium-dependent protease, also blocked 5-HT's effect. Interestingly, whereas chelerythrine blocked maintenance of the enhancement, Bis did not. Because Bis has greater selectivity for conventional and novel isoforms of PKC than for atypical isoforms, this result implicates an atypical isoform in the maintenance of 5-HT's effect. Although induction of enhancement of the Glu-EP requires protein synthesis (Villareal et al., 2007), we found that maintenance of the enhancement does not. Maintenance of 5-HT-dependent enhancement appears to be mediated by a PKM-type fragment generated by calpain-dependent proteolysis of atypical PKC. Together, our results suggest that 5-HT treatment triggers two phases of PKC activity within the motor neuron, an early phase that may involve conventional, novel or atypical isoforms of PKC, and a later phase that selectively involves an atypical isoform.
Collapse
|